Factors affecting the levels of hydrogen peroxide in rainwater

Measurements of hydrogen peroxide (H₂O₂) and several meteorological and chemical parameters were made for 34 rain events which occurred in Miami, Florida between April, 1995 and October, 1996. The measured H₂O₂ concentrations ranged from 0.3 to 38.6 μM with an average concentration of 6.9 μM. A strong seasonal dependence for H₂O₂ concentrations was observed during this period, with highest concentrations in the summer and lower levels in the winter, which corresponds to the stronger solar radiation and higher vaporization of volatile organic compounds (VOCs) in the summer and fall, and the weaker sunlight and lower vaporization in the winter and spring. Measurements also showed a significant increase trend of H₂O₂ with increasing ambient rainwater temperature. Rains that were out from lower latitude were exposed to higher solar irradiation and contained relatively higher levels of H₂O₂ than those from the north. All these observations indicate that photochemical reactions that involved volatile organic compounds are the predominant source of H₂O₂ observed in rainwater. During several individual rainstorms, H₂O₂ concentration was found to increase as a function of time due to electrical storm activities. This finding suggests that lightning could be an important factor that determines the level of H₂O₂ during thunderstorms. Statistical data showed that the highest concentrations of H₂O₂ were observed only in rains containing low levels of nonsea-salt sulfate (NSS), nitrate and hydrogen ion. H₂O₂ concentrations in continental originated rains were much lower than marine originated ones, indicating that air pollutants in continental rains could significantly deplete the H₂O₂ concentration in atmospheric gas-phase, clouds and rainwater.     

Photodegradation of humic acids in the presence of hydrogen peroxide

A batch photoreactor was used to evaluate the UV/H2O2 oxidation process for the removal of humic acids in water. A 450-W UV lamp with high-pressure mercury vapor was employed as the light source. The residues of humic acids and hydrogen peroxide were measured for assessment of process performance and understanding of process reaction behavior. The UV photolysis alone can play an important role in the degradation of humic acids. The presence of hydrogen peroxide was found to promote the degradation efficiency. However, excessive dosage of H2O2 does not further improve the degradation of humic acids. On the contrary, the lower the H2O2 dosage the higher the amount of humic acids which can be removed. Aeration with air does not favor the removal efficiency of humic acids as the oxidation lasts for a sufficiently long time. The presence of carbonate species deteriorates the humic acids' removal, whereas it results in a larger amount of H2O2 decomposition.     

硫化氢吸收净化技术研究进展

综合评述了硫化氢气体的吸收净化方法及特点。净化方法分为干法和湿法两大类。大部分干法脱硫剂均不能再生 ,硫容量相对较低 ,主要适于气体精细脱硫。吸收净化工艺能适应较高负荷的脱硫要求 ,应用面广 ,其中尤以吸收氧化法较突出。指出吸收氧化法中的铁基工艺尽管在工艺控制方面还有一定难度 ,但仍可作为一种有较大发展前途的方法。     

Kinetics of the oxidation of hydrogen sulfite by hydrogen peroxide in aqueous solution:: ionic strength effects and temperature dependence

Conductometry was used to study the kinetics of the oxidation of hydrogen sulfite, HSO⁻₃, by hydrogen peroxide in aqueous non-buffered solution at the low concentration level of 10⁻⁵–10⁻⁶ M, typically found in cloud water. The kinetic data confirm that the rate law reported for the pH range 3–6 at higher concentration levels, rate=k_H·[H⁺]·[HSO⁻₃]·[H₂O₂], is valid at the low concentration level and at low ionic strength I_c. At 298 K and I_c=1.5×10⁻⁴ M, third-order rate constant k_H was found to be k_H=(9.1±0.5)×10⁷ M⁻² s⁻¹. The temperature dependence of k_H led to an activation energy of E_a=29.7±0.9 kJ mol⁻¹. The effect of the ionic strength (adjusted with NaCl) on rate constant k_H was studied in the range I_c=2×10⁻⁴–5.0 M at pH=4.5–5.2 by conductometry and stopped-flow spectrophotometry. The dependence of k_H on I_c can be described with a semi-empirical relationship, which is useful for the purpose of comparison and extrapolation. The kinetic data obtained are critically compared with those reported earlier.     

Enhanced stability of hydrogen peroxide in the presence of subsurface solids

The stabilization of hydrogen peroxide was investigated as a basis for enhancing its downgradient transport and contact with contaminants during catalyzed H(2)O(2) propagations (CHP) in situ chemical oxidation (ISCO). Stabilization of hydrogen peroxide was investigated in slurries containing four characterized subsurface solids using phytate, citrate, and malonate as stabilizing agents after screening ten potential stabilizers. The extent of hydrogen peroxide stabilization and the most effective stabilizer were solid-specific; however, phytate was usually the most effective stabilizer, increasing the hydrogen peroxide half-life to as much as 50 times. The degree of stabilization was nearly as effective at 10 mM concentrations as at 250 mM or 1 M concentrations. The effect of stabilization on relative rates of hydroxyl radical activity varied between the subsurface solids, but citrate and malonate generally had a greater positive effect than phytate. The effect of phytate, citrate, and malonate on the relative rates of superoxide generation was minimal to somewhat negative, depending on the solid. The results of this research demonstrate that the stabilizers phytate, citrate, and malonate can significantly increase the half-life of hydrogen peroxide in the presence of subsurface solids during CHP reactions while maintaining a significant portion of the reactive oxygen species activity. Use of these stabilizers in the field will likely improve the delivery of hydrogen peroxide and downgradient treatment during CHP ISCO.     

Oxidation of chlorophenols with hydrogen peroxide in the presence of goethite

The use of goethite (alpha-FeOOH) and hydrogen peroxide was recently found that they could effectively oxidize organic compounds. The study was to investigate the effect of goethite particle size, goethite concentration, Fe2+ and Fe3+ on the 2-chlorophenol oxidation. Results indicated that 2-chlorophenol can be decomposed with hydrogen peroxide catalyzed by goethite and the oxidation rate increased with decreasing goethite particle size. 2-Chlorophenol degradation was almost retarded with 0.8 g/l of goethite because ferrous ions could not be produced at this condition. Addition of Fe2+ and Fe3+ can enhance the catalytic oxidation rate of 2-chlorophenol very efficiently. In conclusion, the main mechanism of goethite catalyzing hydrogen peroxide to oxidize 2-chlorophenol may be due to the catalysis of ferrous ions and goethite surface.     

硫化氢制氢电解槽设计的改进及实验研究

硫化氢间接电解制氢过程中,在电解槽内采用湍流网结构可以有效地改善传质,基本消除扩散传质的影响。当槽压为1．1V,阴阳极流速皆为200L／h,电解温度为40℃的情况下,电解槽可以长时间保持良好性能,电流密度约为160mA／cm^2。     

Photooxidation of phenol in aqueous solution in the presence of hydrogen peroxide

The combination of ultraviolet light and hydrogen peroxide was demonstrated to be a useful method for removing COD and TOC in aqueous phenol solutions. Both COD and TOC decreased to nearly zero in the presence of hydrogen peroxide.     

硫化氢废气治理研究进展

综合评述了硫化氢废气的各类净化方法及最新的研究进展。硫化氢废气的净化有吸收法、吸附法、氧化法、分解法和生物法。本文对超级克劳斯法和分解法研究进展进行了重点阐述。     

白云石的硫化氢高温脱除性能研究

用天然白云石制备了半焙烧白云石和全焙烧白云石，并在固定床上对这些白云石进行硫化氢的高温脱除性能研究，同时考察了反应温度、空速、粒子粒径对白云石脱硫性能的影响。用X射线衍射（XRD）、热重分析（TG）和气体吸附等测试手段，对脱硫剂的物相组成、结构、比表面积和孔容进行了表征。结果表明，白云石是一种很好的吸硫剂。在同样条件下，3种白云石中半焙烧白云石具有最好的脱硫效果；而对于同一种白云石，反应条件的差异也会导致其脱硫效果的变化。白云石的脱硫性能与其微观结构有密切关系。     

白云石的硫化氢高温脱除性能研究

用天然白云石制备了半焙烧白云石和全焙烧白云石,并在固定床上对这些白云石进行硫化氢的高温脱除性栽能研究,同时考察了反应温度、空速、粒子粒径对白云石脱硫性能的影响.用X射线衍射(XRD)、热重分析(TG)和气体吸附等测试手段,对脱硫剂的物相组成、结构、比表面积和孔容进行了表征.结果表明,白云石是一种很好的吸硫剂.在同样条件下,3种白云石中半焙烧白云石具有最好的脱硫效果;而对于同一种白云石,反应条件的差异也会导致其脱硫效果的变化.白云石的脱硫性能与其微观结构有密切关系.     

Mineralization of CCl4 by the UVC-photolysis of hydrogen peroxide in the presence of methanol

A method for a photochemically induced mineralization of CCl4 is described in which use is made of reductive radicals. The UVC-photolysis (254 nm) of H2O2 added to aqueous solutions of CCl4 is leading to the homolysis of the oxidant yielding hydroxyl radicals (HO) that subsequently react with added methanol to generate hydroxymethyl radicals (CH2OH). The latter radicals initiate mineralization of CCl4 by reductive C-Cl bond splitting. CHCl3, C2Cl4 and C2Cl6 were found as reaction intermediates, but are quantitatively depleted in a parallel oxidative reaction manifold leading to mineralization. Carbon dioxide radical anion, CO2(-), an intermediate in the mineralization pathway of methanol, is also shown to initiate the mineralization of CCl4 by reductive dechlorination. A reaction mechanism is proposed and validated with computer simulations of all the experimental results.     

Partitioning of hydrogen peroxide between the gas and liquid phases in the presence of surfactant

Gas-liquid phase partitioning is a key physical property that can predict the environmental fate of a compound between two phases. Several environmental factors have been known to affect the gas-liquid phase partitioning. We investigated the influence of surfactant on the gas-liquid phase partitioning of hydrogen peroxide (H(2)O(2)). The surfactant used was ammonium perfluorooctanoate (APFO). H(2)O(2) solution containing the surfactant was equilibrated in a closed system and gas phase H(2)O(2) concentration was measured by the peroxyoxalate chemiluminescence (PO-CL) method. Gas phase H(2)O(2) concentrations remained constant below the critical micelle concentration (CMC) and increased linearly with surfactant concentration above the CMC, which indicated that surfactant micelles influenced the gas-liquid phase partitioning of H(2)O(2). This result showed that H(2)O(2)-micelle interactions are less favorable than H(2)O(2)-H(2)O interactions. Surfactant monomers did not affect the gas-liquid phase partitioning of H(2)O(2) due to the absence of micelles. Solvent (methanol) effect was also investigated and showed that gas phase H(2)O(2) concentrations increased with the addition of solvent. This indicated the unfavorable interaction of H(2)O(2) with hydrophobic medium compared to hydrophilic one. It is consistent with the result that H(2)O(2)-micelles has a weaker interaction than H(2)O(2)-water because surfactant micelles are hydrocarbon-like organic phase rather than aqueous phase.     

pH对生物滤池处理含H_2S和NH_3混合恶臭气体的影响

研究了pH对生物滤池处理含H2S和NH3混合恶臭气体的影响,以及不同pH下的物质转化情况和去除机制。结果表明,不同pH下,生物滤池对H2S和NH3的去除率是不同的。在强酸性(pH为2左右)和中性(pH为7左右)条件下,H2S均有较好的去除效果,这分别归于嗜酸性硫细菌和非嗜酸性硫细菌的生物降解作用。低pH下,NH3的去除归于化学中和作用;中性(pH为7左右)条件下,NH3有较高的去除率,主要依靠生物硝化作用。通过考察pH对生物滤池处理效果的影响,确定了生物滤池处理含H2S和NH3混合恶臭气体的pH控制条件和去除机制,为恶臭气体生物处理工艺的选择提供依据。     

发酵产氢的动力学模型

发酵产氢已经建立和应用了一些动力学模型.对描述批次发酵产氢过程的动力学模型,描述各种因子对其影响的动力学模型,以及探讨基质降解速率、产氢细菌(HPB)生长速率和产物形成速率关系的动力学模型进行了综述分析.分析表明,改进的Gompertz模型被广泛用于描述批次发酵产氢过程；Monod模型则广泛应用于描述基质浓度对基质降解...     

生物质催化气化制取富氢燃气的研究

以流化床为反应器 ,探讨了一些主要参数如 :反应器温度 ,水蒸气 ,当量比ER以及催化剂对气体成分、氢产率和潜在氢产率的影响。实验所用催化剂为白云石和镍基催化剂。在实验条件范围内 ,氢产率为 2 2— 83g/kg生物质 (湿基 ) ,潜在氢产率为 115— 2 2 3g/kg生物质 (湿基 )。结果表明 ,较高的反应器温度 ,适当的水蒸气添加量可以有效提高氢的产出 ;白云石和镍基催化剂可使产品气中的氢含量提高 10 %以上。